Circuit protective device



Nov. 3, 1931. P. THEME 3,839,573

I CIRCUIT PROTECTIVE-DEVICE Filed Dec. 2, 1929 e 4 l2 6 /5 k l 0 l4 3 0 EE 0 0 $5 I :2 3

Inventor I Paul Thierne His' Attorney.

Patented Nov. 3, 1931 UNITED STATES PATENT OFFICE PAUL THI'EME, OF BEBLIN-WAIDMANNSLUST, GERMANY, ASSIGNOR TO GENERAL ELEC- TRIO COMPANY, A CORPORATION OF NEW YORK CIRCUIT PROTECTIVE DEVICE Application filed December 2, 1929, Serial No. 411,187, and in Germany December 8, 1928.

My invention relates to circuit protective devices and more particularly to such'devices having thermal responsive meansfor controlling the operation thereof in response to overloads or the like.

In switches having thermic over-currentrelease mechanism a more reliable and effective device results if the circuit of an undervoltage magnet is allowed to be interrupted by the overload responsive thermal element so as to effect the disengagement of a pawl or otherwise effect the opening of the switch. In most cases, the under-voltage magnet is already provided since over-current switches are almost always intended to be operated 1f the voltage of the feed-conductor fails.

However, there are cases in which it is not desired to open the switch in the event of failure ot the voltage and the object of the present invention is to provide a thermic releasing device such that on the occurrence of overcurrent it will interrupt the circuit of the under-voltage magnet, but in its position of rest mechanically locks the armature of the under-voltage magnet in order to prevent a release of the switch it the voltage fails without the simultaneous occurrence of overcurrent.

The single figure of the drawing is a circuit diagram schematically illustrating one embodiment of the invention.

In the drawing 1 designates a bimetallic strip which is heated by a heater 2 energized in accordance with the current in the lines L L to be controlled. The free end 3 of the thermal element is arranged to bend towards one side at a certain temperature. On the free end 3 of the bimetallic strip 1 a contact maker 4 rests, the projection 6 of which is pressed into engagement with the end 3 of the bimetallic strip by a spring 5. In the position of rest illustrated t e contact-maker 4 bridges the terminals 8 and 9 by means of a contact plate 7. Terminals 8 and 9 are connected in the energizing-circuit of the wind ing 10 of the under-Voltage magnet 11. The armature 12 of the under-voltage magnet 11 for the circuit interrupting switch S is-under the influence of a spring 13 which tends to pull it so as to release the latch L holding the switch in the closed position. A locking pawl 14, however, prevents this movement of the armature 12. In addition, the armature 12 of'the under-voltage magnet is held by the magnetic flux generated by the winding 10.

If over-current occurs in the circuit supplied by' conductors L L the bimetallic strip 1 is heated and bends to one side, so that the contact member 4 can follow the pull of the spring 5. Upon the initial movement of the contact-imparting member 4, the projection 15 engages an arm of the pawl 14. and releases the armature 12. Then the bridging contact 7 of the terminals 8 and 9 is disengaged so that the under-voltage magnet 11 no longer retains the armature 12. Thus, after first unlatching the armature and then deenergizing the holding electromagnet, the release of the switch can take place in the known manner, either mechanically by the release of a pawl-device L as illustrated or electrically by switching in a releasing winding. For the sake of simplicity, the releasing winding arrangement has been omitted from the drawing.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A circuit protective switch having a thermal over-current responsive element and an under-voltage operating electrolnagnet characterized in that the energizing circuit of the under-voltage electromagnet is interrupted on the occurrence of over-current by the thermal element and that the armature of the under-voltage electromagnet is normally retained by a locking device which, on the occurrence of over-current is freed bv the thermal element.

2.1m combination, an electroresponsive device, a movable member controlled thereby, separate means for controlling movement of said member, and thermal responsive means for first rendering said separate means ineffective and then controlling the energization of said first electroresponsive means to efiect movement of said member.

3. A circuit protective device comprising means for opening the circuit, electroresponsive means energized from the circuit for controlling the circuit opening means, re-

straining means normally preventing operation of said electroresponsive means, and

thermal current responsive means energized in accordance with the current in the circuit for first rendering said restraining means ineffective and then controlling the energization of said electroresponsive means to efiect operation of the circuit opening means to open the circuit.

m 4. In combination, a circuit interrupter having a normally energized releasing electromagnet, a latch normally preventing operation of said electromagnet, and thermal overload current responsive means for re-' leasing the latch and deenergizing the releasing electromagnet to effect operation of the circuit interrupter.

5. In combination, a circuit interrupter,

a movable member biased to effect operation thereof, a normally energized electromagnet for holding said member against its bias, a

latch. for holding said member against its bias, a separate movable member biased to release said latch and having a contact for deenergizing said holding electromagnet, a thermal responsive latch for holding said separate movable member against its bias and an electrical heater energized in accordance with the current in the circuit controlled by the interrupter for heating said thermal responsive latch.

6. In combination, a normally energized electromagnet, a biased movable magnetic member held thereby against its bias, a latch for holding said member against its bias, and thermal responsive means connected to be energized in accordance with predetermined electrical conditions for first releasing said latch and then controlling the energization of said electromagnet to permit movement of said member in accordance with its bias.

7. A circuit protective device comprising means for opening the circuit, a movable member biased to effect operation of said circuit opening means, a normally energized electromagnet for holding said member against its bias, separate latching means for holding said member against its bias, and thermal responsive means for first rendering,

said latching means ineffective and then controlling the energization of said electromagnet to release said member for movement in accordance with its bias.

In witness whereof, I have hereunto set my hand this 16th day of November, 1929. PAUL THIEME. 

